Metered pulse pump

ABSTRACT

A metering pulse pump for metering an additive liquid into a liquid carrier under high pressure includes a rapidly reciprocating piston pump having a number of pumping chambers and having an inlet connectable to a source of liquid and an outlet, and an outlet line carrying liquid from the outlet under high pressure; a source of additive liquid; a differential piston pump having an inlet connectable to the source of additive liquid, an inlet check valve, a pumping chamber, an outlet check valve, and an outlet connected to the outlet line; and a connection from one of the reciprocating pump pumping chambers to the differential piston pump feeding high-pressure liquid to start the pumping stroke of the differential piston pump. In one embodiment, a spring is used to return the differential piston on its intake stroke. In a second embodiment, a connection from another of the reciprocating pump pumping chambers, which is out of phase with the first chamber, is used to return the differential piston on its intake stroke.

BACKGROUND OF THE INVENTION

Rapidly reciprocating piston pumps are used to pump high-pressure fluid for a variety of purposes. It is also sometimes necessary to insert a chemical additive into the high-pressure fluid stream. However, when such additives are corrosive, they should not be pumped by the primary pump. Instead, a secondary, metering pump is used to pump the additive liquid.

Various devices have been employed for automatically metering small amounts of an additive liquid to the mainstream of a liquid carrier. When the liquid carrier is under high pressure, however, highly sophisticated and hence expensive metering pumps such as gear pumps ordinarily are employed. An inexpensive apparatus which would permit an additive liquid to be metered to a liquid carrier under high pressure is much to be desired.

A Metering Pulse Pump is disclosed in U.S. Pat. No. 3,930,756. However, this pulse pump uses a diaphragm pump to pump the additive liquid to the mainstream of the liquid carrier. Such diaphragm pumps are prone to early failure. It also requires a pressure-relief valve to regulate the pressure of the metering pulse pump and the speed of the pump and length of its stroke.

There is a need for an improved metering pulse pump that overcomes the above problems.

SUMMARY OF THE INVENTION

A metering pulse pump for metering an additive liquid into a liquid carrier under high pressure, the pump comprising:

-   -   a rapidly reciprocating piston pump having a plurality of         pumping chambers and having an inlet connectable to a source of         liquid and an outlet, and an outlet line carrying liquid from         the outlet under high pressure;     -   a source of additive liquid;     -   a differential piston pump having an inlet connectable to the         source of additive liquid, an inlet check valve, a pumping         chamber, an outlet check valve, and an outlet connected to the         outlet line; and     -   a connection from one of the plurality of reciprocating pump         pumping chambers to the differential piston pump feeding         high-pressure liquid to start the pumping stroke of the         differential piston pump.

A principal object and advantage of the present invention is that the differential piston pump has a longer life than a diaphragm pump used previously.

Another principal object and advantage of the present invention is that it is simpler than earlier metering pulse pumps.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a first embodiment of the metering pulse pump of the present invention.

FIG. 2 is a cross-section taken at approximately the lines 2 of FIG. 1, during the pumping stroke.

FIG. 3 is similar to FIG. 2, taken during the return stroke.

FIG. 4 is a perspective view of a second embodiment of the metering pulse pump of the present invention.

FIG. 5 is a cross-section taken at approximately the lines 5 of FIG. 4, during the pumping stroke.

FIG. 6 is similar to FIG. 5, taken during the return stroke.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The metering pulse pump of the present invention is generally shown in the Figures as reference numeral 10.

The metering pulse pump 10 is used for metering an additive liquid (such as a chemical) into a liquid carrier which is under high pressure.

The metering pulse pump 10 comprises a rapidly reciprocating piston pump 20 having a plurality of pumping chambers 22 a, 22 b, 22 c etc. and also having an inlet 24, a source 26 of additive liquid and an outlet 28, and also comprising an outlet line 29 carrying liquid from the outlet 28 under high pressure. A pump 20 which may be used in the present invention is disclosed in U.S. Pat. No. 3,930,756, herein incorporated by reference. However, this earlier pump suffers from the disadvantage of being prone to earlier failure because of its use of a diaphragm pump and also of being complex because of the need for a pressure relief valve to regulate the pressure in the pumping chamber.

The present invention comprises the following changes to the previously described rapidly reciprocating piston pump 20.

A differential piston pump 30 has an inlet 32 connectable to the source 26 of additive liquid. The differential piston pump 30 further comprises a pumping chamber 42. An inlet check valve 40 is inserted between the inlet 32 and the pumping chamber 42. The differential piston pump 30 further comprises an outlet check valve 44, and an outlet 46 connected to the outlet line 29 of the rapidly reciprocating piston pump 20.

A connection 50 is made from one of the plurality of pumping chambers 22 a, 22 b, 22 c, etc. to the differential piston pump so that high-pressure liquid from the rapidly reciprocating piston pump 10 can be used to start the pumping stroke of the differential piston pump 30 as will be further described.

In further detail, the differential piston pump 30 further comprises a differential piston 34, having a first portion 34 a and a second portion 34 b, the first portion 34 a having a larger surface area than the second portion 34 b. The differential piston 34 reciprocates in the pumping chamber 42.

A first embodiment of the present invention is shown in FIGS. 1-3.

In the first embodiment, the differential piston pump 30 further comprises a spring 36 biasing the differential piston 34 toward its return stroke. In this embodiment, the pumping chamber 42 may enclose the spring 36, as shown.

Operation of the first embodiment is as follows.

As shown in FIG. 2, during the pumping stroke of one of the plurality of pumping chambers 22 a, 22 b, 22 c etc. of the rapidly reciprocating piston pump, high-pressure fluid is forced against the first portion 34 a of the differential piston pump 34. At this same moment, the pumping chamber 42 of the differential piston pump 34 is encountering high-pressure from the fluid in the outlet line of the rapidly reciprocating piston pump. These pressures may be approximately equal. However, high-pressure fluid in the pumping chamber 42 encounters the portion 34 b having a smaller surface area than the portion 34 a.

The operating principle of a differential piston having an inlet pressure Pi, an outlet pressure P_(o), an inlet piston area A_(i), and an outlet piston area A_(o) is that P_(o)/P_(i)=A_(i)/A_(o).

Under this operating principle, the difference in surface areas between the first portion 34 a and the second portion 34 b will cause the piston 34 to be biased toward the outlet 46, thus allowing the pressure from the first of the plurality of pumping chambers 22 a, 22 b, 22 c. etc. to force the piston against the spring 36 and the pressure in the outlet 46, thus pumping additive liquid into the outlet line 29.

As shown in FIG. 3, during the return stroke of the differential piston 34, additive liquid is drawn into the pumping chamber 42 by vacuum. Pressure from the pumping chamber of the reciprocating piston pump is low, as that chamber is now filling with liquid. The spring 36 can then force the differential piston 34 away from the pumping chamber 42, thus drawing additive liquid into the pumping chamber 42.

In the second embodiment, shown in FIGS. 4-6, rather than having a spring 36 biasing the differential piston 34 toward its return stroke, the differential piston pump 30 further comprises a connection 60 from another of the plurality of reciprocating pump pumping chambers 22 a, 22 b, 22 c., etc. to the differential piston pump 30. It will be clear from a study of U.S. Pat. No. 3,930,756 that the pumping chambers 22 a, 22 b, 22 c., etc. are out of phase from each other. That is, for example, as chamber 22 a is pumping high-pressure primary liquid, another chamber 22 c will be on its intake stroke. Conversely, as chamber 22 a is on its intake stroke, chamber 22 c is pumping high-pressure primary liquid.

In the second embodiment, high-pressure liquid from chamber 22 a, for example, is fed through the connection 50 to the differential piston pump 34, and high-pressure liquid from chamber 22 c, for example, is fed through connection 60 to the differential piston pump 34. As shown in FIGS. 5 and 6, high-pressure liquid from the connection 50 engages the first portion 34 a of the differential piston 34, while high-pressure liquid from the connection 60 engages the second portion 34 b of the differential piston 34.

Operation of the second embodiment is as follows.

As shown in FIG. 5, during the pumping stroke of one of the plurality of pumping chambers 22 a, for example, of the rapidly reciprocating piston pump, high-pressure fluid from the connection 50 is forced against the first portion 34 a of the differential piston 34. At this same moment, the pumping chamber 42 of the differential piston pump 34 is encountering high-pressure from the fluid in the outlet line of the rapidly reciprocating piston pump. These pressures may be approximately equal. However, high-pressure fluid in the pumping chamber 42 encounters only the difference between the surface areas of the portion 34 a and portion 34 b. This differential may be made as small as necessary to overcome the pressure in the outlet 46.

This differential will cause the piston 34 to be biased toward the outlet 46, thus allowing the pressure from the first of the plurality of pumping chambers 22 a, for example, through the connection 50 to force the piston against the pressure in the outlet 46, thus pumping additive liquid into the outlet line 29. The pressure in connection 60 from chamber 22 c, for example, is low.

As shown in FIG. 6, during the return stroke of the differential piston 34, additive liquid is drawn into the pumping chamber 42 by vacuum. Pressure from the pumping chamber 22 a of the reciprocating piston pump through the connection 50 is low, as that chamber is now filling with liquid. However, pressure from the pumping chamber 22 c through the connection 60 is now high, and forces the differential piston 34 away from the pumping chamber 42, thus drawing additive liquid into the pumping chamber 42.

The operation of the inlet check valve 40 and outlet check valve 44 is as known, to coordinate with the pumping stroke and the return stroke of the differential piston 34.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar to or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety to the extent allowed by applicable law and regulations. In case of conflict, the present specification, including definitions, will control.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention. 

1. A metering pulse pump for metering an additive liquid into a liquid carrier under high pressure, the pump comprising: (a) a rapidly reciprocating piston pump having a plurality of pumping chambers and having an inlet connectable to a source of liquid and an outlet, and an outlet line carrying liquid from the outlet under high pressure; (b) a source of additive liquid; (c) a differential piston pump having an inlet connectable to the source of additive liquid, an inlet check valve, a pumping chamber, an outlet check valve, and an outlet connected to the outlet line; and (d) a connection from one of the plurality of reciprocating pump pumping chambers to the differential piston pump feeding high-pressure liquid to start the pumping stroke of the differential piston pump.
 2. The apparatus of claim 1, wherein the differential piston pump further comprises a differential piston having a first portion and a second portion, the differential piston reciprocating in a chamber, the first portion having a larger surface area than the second portion.
 3. The apparatus of claim 2, further comprising a spring biasing the differential piston pump toward its return stroke.
 4. The apparatus of claim 3, wherein high-pressure liquid from one of the plurality of reciprocating pump pumping chambers engages the first portion and wherein high-pressure liquid in the outlet line engages the second portion, the difference in surface areas between the first portion and the second portion biasing the differential piston to pump the additive liquid into the outlet line.
 5. The apparatus of claim 1, further comprising a connection from another of the plurality of reciprocating pump pumping chambers to the differential piston pump feeding high-pressure liquid to start the return stroke of the differential piston pump.
 6. The apparatus of claim 5, wherein the first portion is engaged by liquid from one of the plurality of reciprocating pump pumping chambers, the second portion engages liquid from another of the plurality of reciprocating pump pumping chambers, and wherein liquid pressures in each of the reciprocating pump pumping chambers vary inversely.
 7. The apparatus of claim 4, wherein the first portion directly contacts high-pressure liquid from one of the plurality of reciprocating pump pumping chambers.
 8. The apparatus of claim 7, wherein the second portion directly contacts high-pressure liquid in the outlet line.
 9. In a rapidly reciprocating piston pump having a plurality of pumping chambers and having an inlet connectable to a source of liquid and an outlet, and an outlet line carrying liquid from the outlet under high pressure, the improvement comprising: (a) a source of additive liquid; (b) a differential piston pump having an inlet connectable to the source of additive liquid, an inlet check valve, a pumping chamber, an outlet check valve, and an outlet connected to the outlet line; and (c) a connection from one of the plurality of reciprocating pump pumping chambers to the differential piston pump feeding high-pressure liquid to start the pumping stroke of the differential piston pump.
 10. The apparatus of claim 9, wherein the differential piston pump further comprises a differential piston having a first portion and a second portion, the differential piston reciprocating in a chamber, the first portion having a larger surface area than the second portion.
 11. The apparatus of claim 10, further comprising a spring biasing the differential piston pump toward its return stroke.
 12. The apparatus of claim 11, wherein high-pressure liquid from one of the plurality of reciprocating pump pumping chambers engages the first portion and wherein high-pressure liquid in the outlet line engages the second portion, the difference in surface areas between the first portion and the second portion biasing the differential piston to pump the additive liquid into the outlet line.
 13. The apparatus of claim 10, further comprising a connection from another of the plurality of reciprocating pump pumping chambers to the differential piston pump feeding high-pressure liquid to start the return stroke of the differential piston pump.
 14. The apparatus of claim 13, wherein the first portion is engaged by high-pressure liquid from one of the plurality of reciprocating pump pumping chambers, the second portion engages high-pressure liquid from another of the plurality of reciprocating pump pumping chambers, and wherein liquid pressures in each of the reciprocating pump pumping chambers vary inversely. 